Mid-infrared Imaging of SR 12 c with JWST/MIRI: Grain Growth in an Evolved Circumplanetary Disk

Abstract: The physical properties of circumplanetary disks offer insights into the formation of giant planets and their satellites. The circumbinary planetary-mass companion SR 12 c (1200 au from SR 12 AB) hosts an isolated dust disk directly detected with ALMA. We present JWST/MIRI imaging of SR 12 c from 5.6 to 21 $μ$m and analyze its spectral energy distribution from infrared to submillimeter wavelengths. Phenomenologically, the dust disk can be described by a two-component blackbody with large contrasts in characteristic temperatures and radii. Physically motivated models with varied geometries and heating mechanisms suggest a predominantly flat, irradiation-heated disk with a smaller contribution from viscous dissipation. The disk is inferred to be compact, with an inner radius of ~3 $R_{\rm Jup}$. The outer radius is only loosely constrained, with a characteristic value of ~3 au. The lack of strong 10 $μ$m excess emission suggests significant grain growth and dust settling. We also find that SR 12 c is broadly consistent with the empirical star-disk scaling relations, providing context for its possible formation pathway. These results demonstrate the power of combining mid-infrared and submillimeter observations with disk modeling to better understand the physical properties of circumplanetary disks.